Drill



INVENTOR March 27, 1934. F. K. LANDGRAF I. DMLL Filed Nov. 19. 1981 N iw H Patented Mar, 27, 1934 DRILL Frederick K. Landgraf, Grafton, Pa.,asaignor to Flannery Bolt Company, Pittsburgh, Pa., a corporation ofDelaware Application November 19, 1931, Serial No. 576,072

4 csims.

The invention relates to multiple-part rock drills of the type in whichbits are detachably fastened to drill rods by screw thread connections.

5 As commonly constructed, rock drills of the type herein'contemplatedconsist of a drill rod ofl a length suitable for the particular holebeing drilled, an internally threaded coupling sleeve engaging threadson the outer end of the rod,

and a short detachable bit threaded to be engaged by the coupling. At ornear its center the coupling is frequently provided with an inwardlyextending shoulder intended to limit the distances the bit and rod canbev screwed into it and at their ends the bit and rod are provided withabuttingprojections of smaller diameter than the bore of the couplingshoulder and intendcd to prevent either the rod or bit from becomingscrewed tightly against the shoulder.

In the operation of a drill hammer, the drill rod is normally rotated ina direction tending to tighten its threaded connection to the couplingand that of the coupling to the bit, left hand being customarily used.-If the shoulder and projection construction, just explained, preventstightening of these connections, there is such 'looseness between theseveral inter-engaging threads as to permit ingress of the dust or slimeof drilled rock, which, on account of the rapid drilling vibrations,quickly abrades the threads particularly when abrasive rock is beingdrilled. Even in the absence of dust, slime or other abrasive materialbetween the threads, substantial abrasion of the threads may result fromthe rapid drilling vibrations. This abrasion is not of materialconsequen'ce as far as concerns the bit and coupling because they arerelatively small, cheap and easily renewable members. I'Iowever,I whenthe threads at the end of a drill 40 rod become abrarled it is necessaryto re-thread it because the rod is a relatively expensiv'e memberintended for long life and can not economically be discarded merely onaccount of its threadsbeing abraded. This re-threading involvesconsiderable expense and loss of time because it is necessary to sendthe rod from the ileld to a machine shop to have its wom thread removed,a new thread put on, and the end of the rod heat treated to give it itsrequired resistance to fatigue. If in the operation of a drill a bitbecomes tightly screwed in a coupling, as not infrequently happensregardless of the above-explained instrumentalities intended to preventit, it is then necessary to apply wrenches or other tools to the bitandcoupling to loosen them, which is timeconsuming and defeats animportant advantage of a multiple-part drill, namely, the readydetachability of bits. The importance of this becomes apparent whenconsideration is given to the fact that ordinarily a bit does not drillvery to many minutes in hard rock before its drilling edges are so wornthat it must be replaced.

The objects of this invention are to improve the connections of theparts of multiple-part drills of the character explained, to the .endthat the 65 threads on rods will not become rapidly abraded by theoperation of drills, and to the further end that bits may be quickly andeasily removed and replaced.

The invention is illustrated in the accompanying drawing, of which Fig.1 is a side view of an assembled drill; Fig. 2 a side view showing thecoupling member in longitudinal central section; and Fig. 3 a viewcorresponding to Fig. 2 with the bit and drill rod detached from thecoupling.

The drill provided according to this invention comprises a bit 1, adrill rod 2 and a coupling 3. As far as concerns the form of itscutters, the bit may be of any desired construction. While the couplingmay be of various forms, it is prefao erably an interiorly threadedsleeve of the general type illustrated. As far as concerns its generalconstruction, the drillirod may be vof the familiar type provided with acentral bore for the passage of compresscd air through it, and throughthebit, for the usual purpose.

For connecting coupling 3 to rod 2, these members are provided withcooperating threads formed to prevent relative abrasion-producingmovements between the members. For this pur- -l pose these members areprefcrably provided with tapered threads, rod 2 being provided with anextemal tapered thread 5, and coupling 3 'with a cooperating intemaltapered thread 6.' While various forms of tapered threads may be used, fthey are prefcrably of the undulatory and continuously curved typedisclosed in Patent No. 1,642,183 to F. W. Thurston with the attendingadvantages .dscribed in that patent. By providing the end of the drillrod and the end of the coupling attached to 'it with cooperating taperedthreads, the operation of the drill hammer screws these memberssoitightly together that there is no loose play between them and little,if any, possibility of abrasive material get- 1 ting between them.Consequently. the threads of the rod do not become abraded, even thoughsome rock dust may be lodged between these parts when they are screwedtogether.

For connecting bit 1 to couqlina 3, these mem- 'the bit to becometightly bers are provided with threads formed to readily permit the bitto be removed from the coupling, and with greater ease than the removalof the coupling from the rod. For this purpose, the shank of the bit ispreferably provided with an extemal straight thread 10, and the couplingwith cooperating internal straight thread 11, these threads being ofgreater lead than the co- Operating tapered threads 5 and 6 of the rodand coupling. For ease in the securing of the relatively steep lead ofthe cooperating bit and coupling threads, a plurality of threads arepreferably used, two being shown in the illustrative embodiment of theinvention. These threads are also preferably of the undulatory andcontinuously curved contour disclosed in the above mentioned patent toThurston.

To prevent a bit from becoming screwed tightly in coupling 3, the end ofrod 2 is provided with a projection 15, which, when the coupling isscrewed upon the rod as shown in' Fig. 2, extends beyond the inner endof coupling thread 6 to form an abutment for the inner end of thethreaded shank of the bit. Accordingly, the bit is continuously held inits relatively loose threaded engagement with the coupling.

In the operation of a multiple-part drill of the type herein disclosed,the customary rotation of a drill rod by a drill hammer tends tocontinuously tighten the coupling upon the end of the rod, and toscrewthe bit into the coupling. The tightening of the coupling upon theend of the rodV is not resisted except by their cooperating taperedthreads, and accordingly a tight screw connection is continuouslymaintained which prevents abrasion-producing relative movements betweenthe rodand coupling. The tendency of screwed in the coupling isresistedw'by the abutting of the end of the shank of the bit"againstprojection 15 on the drill rod, so that the bit does not become screwedtightly into the coupling and may be readily removed at any time by afew turns of the bit. Furthermore, on account of the greater steepnessof the co- Operating threads of the bit and coupling than those of thecoupling and rod. the latter become tightened more readily than theformer during drilling Operations, which is an additional assurance ofdesirable tightness between the threads of the coupling and rod, and ofdesirable looseness between those of the coupling and bit.

lcoupling and bit being A further advantage of the invention attendingthe provision of a tapered thread on the end of a drill rod is that therod may be `advantageously thickened at and adjacent to its end toreceive the thread and also to increase the resistance of this portionof the rod to breakage, it being understood that the weakest point ofthe rod is-at or near the threaded end where it is subjected to maximumstresses However, the invention is fully applicable to rods having plainends.

According to the provisions of the patent statutes, I have explained theprinciple and operation of my invention, and have illustrated what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

I claim:

1. A drill comprising a bit, a drill rod,'and a threaded couplingconnecting the bit to the rod, the coupling and rod being provided withcooperating tapered threads, and the coupling and bit being providedwith cooperating straight threads of greater lead than said taperedthreads.

2. A drill comprising a bit, a drill rod, an interiorly threadedcoupling sleeve connecting the bit to the rod, the coupling and rodbeing provided with cooperating tapered threads, and the provided withcooperating straight threads of greater lead than said tapered threads.

3. A drill comprising a bit, a drill rod, and a coupling having separatethreads connecting the bit to the rod, the cooperating threads of thecoupling and bit being double and of greater lead than those of thecoupling and rod to facilitate the removal of the bit from the coupling.

4. A drill comprising a bit, a drill rod, and an interiorly threadedcoupling connecting the bit to the rod, the coupling and rod beingprovided with cooperating tapered threads formed to prevent relativeabrasion-producing movements between the coupling and rod duringdrilling operations, and the coupling and bit being provided with aplurality of cooperating straight threads of greater lead than saidtapered threads to facilitate the removal of the bit from the cou-Dling.

' FREDERICK K. LANDGRAF.

